The present invention relates generally to shielding and, more particularly, to devices for shielding electronic components and/or circuitry within electronic devices.
Printed circuit boards (PCBs) are widely used electronic substrates in the electronics and telecommunications industry. PCBs generally include one or more layers of an insulating substrate (e.g., plastic) on which an electrical circuit is formed by depositing a predetermined pattern of a conducting metal (e.g., copper) for connecting various electronic components (e.g., semiconductors) which are mounted on or embedded in the PCB layers. Many of these electrical circuits include components which operate at a high radio frequency (RF). The RF emissions from these components can interfere with the proper operation of other components or circuits in the vicinity of the PCB. Thus, it may be important to block or shield these RF emissions in order to prevent RF interference.
For compact electronic devices, such as radiotelephones, a PCB serving as a ground plane may be utilized as a part of a shielding system. A conductive housing (often referred to as a xe2x80x9cshield canxe2x80x9d) that is configured to surround all or part of a component is typically electrically connected to a PCB upon which the component is secured. An exemplary shield can that is electrically secured to a PCB is described in co-assigned U.S. Pat. No. 5,847,938.
Conventional shield cans can have somewhat complex shapes and configurations because of PCB space constraints within small electronic devices such as radiotelephones. Referring to FIG. 1, an exemplary shield can 10 with a somewhat complex configuration and that is configured to be secured to a PCB 12 over a plurality of electronic components 14 is illustrated. The illustrated shield can 10 includes a top 16 and a plurality of side walls 18 depending from the top 16.
During the development stage of an electronic device, such as a radiotelephone, the location, shape and/or size of electronic components and circuitry on a PCB therewithin may change. Accordingly, any such changes may require a change in the size and/or configuration of a device, such as a shield can, for shielding these components and circuitry. Unfortunately, changing the size and/or configuration of a shielding device during the development phase of an electronic device may lead to increased costs and may cause development delays. As a result, conventional shield cans that are molded or formed for a specific location and/or configuration may be unsuitable for use during the development stages of an electronic device.
In view of the above, it is therefore an object of the present invention to provide an RF shielding apparatus for shielding electronic components and circuitry mounted to a PCB within an electronic device that can be easily modified in shape and configuration during the development stage of the electronic device.
It is another object of the present invention to facilitate the use of shielding devices within electronic devices, such as radiotelephones, where PCB space may be limited.
It is another object of the present invention to facilitate reducing costs associated with electronic device development.
These and other objects of the present invention are provided by an electromagnetic shielding apparatus that can be easily modified in shape and configuration to facilitate electronic device development. An electromagnetic shielding apparatus, according to one embodiment of the present invention, includes an electronic substrate having a surface and a ground trace extending along the surface to define a perimeter of an area of the electronic substrate to be shielded. A plurality of electrically conductive block members are electrically secured to the ground trace in adjacent relationship. Each electrically conductive block member includes opposite front and back faces, a pair of opposite side faces, and generally parallel top and bottom faces. An electrically conductive cover is electrically secured to the top face of each of the block members to overlie the area of the electronic surface to be shielded.
The present invention can be advantageous during the development phase of electronic devices when the locations of electronic components and circuitry are being determined because the block members can be arranged on a PCB in virtually any desired pattern. Similarly, a cover can be fabricated with virtually any desired shape to overlie the block members so as to form an enclosure around an area of a PCB to be shielded.
According to another embodiment of the present invention, a groove may be formed in a bottom face of a block member so as to extend between the front and back faces thereof. Accordingly, a conductive trace can extend along a PCB through the groove and across the perimeter of the shielded area.
According to another embodiment of the present invention, a shielding apparatus may be incorporated into PCMCIA cards (also known as xe2x80x9cPC cardsxe2x80x9d). A PCMCIA card includes a housing having an electrically conductive cover and a PCB disposed within the housing. The PCB includes a surface and a ground trace extending along the surface to define a perimeter of an area of the PCB to be shielded. A plurality of electrically conductive block members are electrically secured to the ground trace in adjacent relationship. The housing cover is electrically secured to a top face of each of the block members. The housing cover thus forms a shielding enclosure for the area of the PCB defined by the conductive blocks.
The present invention when utilized within a PCMCIA card can be advantageous over previous shielding methods utilizing PCMCIA card spring fingers. PCMCIA card spring fingers often have a tendency to deform the cover of a PCMCIA card. Furthermore, PCMCIA card spring fingers can be difficult to install with automated xe2x80x9cpick and placexe2x80x9d equipment.